Rigging Automatic Weight not working right
To answer your question, your weighting is now entirely off, but you can fix it via weight painting. The parts you want to move should be red, with a bit of a falloff into yellow and green as it merges into the other bone.

HOWEVER, since you've sculpted, and it's not intended for animation, there's a much easier solution. Try using a lattice! Add a lattice to your scene and move and scale it around to fit the arm as well as you can (do not do this in edit mode! it'll mess up your results!). Then apply a lattice modifier to your sculpt, and select the lattice you just made. Now you can go into edit mode. Before you touch anything, add some more points to work with over in the modifier settings until you have enough to bend it. It shouldn't take many. Now all you have to do is move the lattice around until it looks like you want.